The present exemplary embodiment relates generally to fusing of images in a printing system including a plurality of marking engines. It finds particular application in conjunction with a printing system which includes first and second tandem marking engines where the second marking engine receives print media which has been partially fused by the fuser of the first marking engine, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications.
In a typical xerographic marking engine, such as a copier or printer, a photoconductive insulating member is charged to a uniform potential and thereafter exposed to a light image of an original document to be reproduced. The exposure discharges the photoconductive insulating surface in exposed or background areas and creates an electrostatic latent image on the member, which corresponds to the image areas contained within the document. Subsequently, the electrostatic latent image on the photoconductive insulating surface is made visible by developing the image with a developing material. Generally, the developing material comprises toner particles adhering triboelectrically to carrier granules. The developed image is subsequently transferred to a print medium, such as a sheet of paper. The fusing of the toner onto the paper is generally accomplished by applying heat to the tonerwith a heated roller and application of pressure.
Systems which incorporate several marking engines have been developed. These systems enable high overall outputs to be achieved by printing portions of the same document on multiple printers. Such systems are commonly referred to as “tandem engine” printers, “parallel” printers, or “cluster printing” (in which an electronic print job may be split up for distributed higher productivity printing by different printers, such as separate printing of the color and monochrome pages). Tandem engine printing systems allow a sheet of print media to be printed by a first marking engine and then conveyed by a paper pathway to a second marking engine. This permits “tandem duplex printing.” In this process, a first marking engine applies an image to a first side of a sheet and a second marking engine applies an image to a second side of the sheet. Each of the marking engines is thus operating in a simplex mode to generate a duplex print.
Such integrated printing systems have advantages over more complex, single marking engine systems in that they can achieve high productivity by combining several relatively low-cost smaller marking engines. However, the smaller marking engines frequently do not have the capability to fuse a wide range of print substrates or may run at lower outputs, in terms of prints per minute, when certain heavyweight media is to be fused.